Device for detecting and displaying the response of a tissue to stimuli

ABSTRACT

A tissue electrochemical response detector includes a probe input electrically engaging the tissue, a detector circuit, and an output device. Changes in the probe impedance due to electrochemical variations in the tissue are sensed by the detector circuit and an audible or visible signal indicative of the variation is supplied by the output device.

United States Patent Volberg [54] DEVICE FOR DETECTING AND DISPLAYINGTHE RESPONSE OF A TISSUE TO STIMULI [72] Inventor: Herman W. Volberg,PO. Box 125,

Oahu, Hawaii 96734 [22] Filed: Sept. 9, 1970 [21] Appl. No.: 70,702

[52] US. Cl. ..'....340/421, 73/73, 324/61 M, 324/65 M, 340/233,340/235, 340/384 E [51] Int. Cl. ..G08b 21/00 [58] Field ofSearch.340/235, 421, 384 E; 324/61 M, 324/65 R, 65 M; 73/73 [56]References Cited UNITED STATES PATENTS 2,812,757 1 1/1957 Lusk et a1...340/235 UX 3,493,950 2/1970 Lind ..324/65 X 3,531,684 9/1970 Nuckolls..340/235 UX 3,284,796 11/1966 Borsattino et al ..340/384 E DETECTORAMPLIFIER 2o 22 OUTPUT 1 Aug.29, 1972 Gebhart ..324/61 M PrimaryExaminer-David L. Trafton Attorney-Owen, Wicker-sham and Erickson [57]ABSTRACT A tissue electrochemical response detector includes a probeinput electrically engaging the tissue, a detector circuit, and anoutput device. Changes in the probe impedance due to electrochemicalvariations in the tissue are sensed by the detector circuit and anaudible or visible signal indicative of the variation is supplied by theoutput device.

llClaims,5DrawingFigures PHENTEDauszs mm SHEET 2 0F INVENTORQ HERMAN W.VOLBERG ATTORNEYS DEVICE FOR DETECTING AND DISPLAYING THE REsPoNs or Arrssus T STIMULI BACKGROUND OF THE INVENTION The present inventionrelates generally to detectors and more particularly to a biologicaldetector capable of sensing electrochemical variations in tissue andsupplying an output indicative thereof. In connection with the study ofbiological organisms there is often a need to look at changes in theelectrochemical status of a particular tissue. For example, work hasbeen done recently to determine if plants are able to perceive, feelemotion and the like by studying changes in the electrochemical statusof some tissue of the plant as a result of external stimulation.However, it is a problem to accurately determine changes in theelectrochemical status of plant. This is aggravated by the necessity ofdistinguishing between electrochemical changes and changes in ambientconditions. Thus it is an object of this invention to provide a solutionto the foregoing problem.

It is a further object of this invention to provide a device foraccurately detecting variations in the electrochemical status of tissue.

It is another object of this invention to provide a device that willprovide a visual output indicative of changes in the electrochemicalstatus of plants.

It is yet another object of this invention to provide a device capableof supplying an audible output indicative of changes in theelectrochemical status of plants.

Finally, it is an object of this inventionto provide a device capable ofdistinguishing between changes in electrochemical status and changes inambient conditons.

SUMMARY OF THE INVENTION These and other objects of the invention areachieved by a detector device that is electrically connected to a tissueof interest and that provides anoutput indicative of any electrochemicalvariations therein. A sensor element electrically engages the tissue andis communicable with the input to a detector circuit designed togenerate an electrical signal related to any change in theelectrochemical status'of the tissue. The electrical signal in turnstimulates an output device that supplies either an audible and/orvisual indication of any change in electrochemical status.

According to another aspect of the invention, the detector circuit ismade adjustable to compensate for relatively low frequency changes inthe ambient conditions, and means may be connected to the detectorcircuit for making adjustments automatically.

Finally, the invention, includes several specific circuits as preferredembodiments.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a block diagram illustratingthe functional organization of the invention;

FIG. 2 is a circuit diagram of a preferred embodiment of the inventionwith a visual output;

FIG. 3 is a circuit diagram of an alternative embodiment of theinvention having an audible output;

' FIG. 4 is an elevational view of'how one embodiment of the inventionmight look when applied to a plant; and

FIG. 5 is a circuit diagram of an automatic compensation scheme.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic conceptual frameworkof the invention is illustrated in FIG. 1. There,a leaf 10 iselectrically contacted by a sensor consisting in this case of two fiatplate electrodes 12 and 14 that are in turn connected via coaxial cable16 to a detector 18. Variations in the electrochemical status of leaf 10appear at detector 18 as a change in the impedance of electrodes 12 and14. When an electrochemical change has occurred, a small signal isgenerated in response thereto by detector 18 and is transmitted toamplifier 20. The amplified signal then stimulates an output device 22which informs the human agency of the electrochemical change. Outputdevices may take the form of a graph, meter, lights, 7

In applying electrodes 12 and 14 to a leaf, it is helpful I to firstblot away excessive moisture and then to insert a piece of sterile gauzeimpregnated with agar-agar gelatin between each electrode and the leaf.This practice avoids shunting effects, cushions the contact, and reducesthe Ieaf-to-electrode resistance.

A more detailed embodiment of the invention is shown in FIG. 2 where-aclip-on probe 24'is used to electrically engage the tissue of interest.A coaxial cable 26 connects probe 24 to a bridge circuit 28 having fixedimpedance legs 30 and 32, variable impedance leg 34, and the unknownimpedance leg 36. For adjusting the sensitivity of the circuit, variableresistance 38 is in parallel with the unknown impedance. Power issupplied to bridge 28 from a dc power supply 40 via leads 42 and 44.

Points 31 and 33 may be considered the output of bridge 28 and areconnected respectively to the gates of PNP transistors 46 and 48. Thecollectors of transistors 46 and 48 are connected through resistors 50and 52 respectively to the negative side of power supply 40. Theemitters of transistors 46 and 48 are connected via thermalstabilization resistors 54, 56, and 5 8 to the positive side of powersupply 40. Transistors 46 and 48 form a first stage in the amplificationcircuitry. The outputs therefrom are taken at points 58 and 60 and areconnected respectively to the bases of NPN transistors 62 and 64.Resistor 66 interconnects the positive side of power supply 40 with thecommon collector of transistors 62 and 64, while resistors 68 and 70respectively connect the emitters thereof to the negative side of powersupply 40. The emitters of transistors 62 and 64 and are also connectedrespectively to the bases of PNP transistors 72 and 74 which form thefinal stage of amplification. Connected between the collectors of thelatter transistors and the negative side of power supply 40 are lightsource 76 and resistor 78 and light source 80 and resistor 82,respectively, completing the circuit connections. Transistors 72 and 74have a common emitter connected through resistor 66 to the positive sideof power supply 40. I

Transistors 46, 64, and 72 are complementarily coupled in cascade anddrive light source 76 with a voltage proportional to that at point 31.Amplifiers 48, 62, and 74 are also complementarily coupled in cascadeand drive light source 80 with a voltage proportional to that at point33.

In operation, clip probe 24 is electrically attached to a tissue ofinterest. Variable resistor 34 is then adjusted to balance bridge 28 sothat the voltage level at points 31 and 33 are the same. Bridgesensitivity is enhanced by adjusting variable resistance 38to make thetotal impedance of leg 36 approximately equal to that in each of theremaining legs. 6

After the bridge is balanced and before any change in electrochemicalstatus has occurred in the tissue, the voltage levels at points 31 and33 will be exactly the same and consequently the voltages applied tolight sources 76 and 80 will be as close to the same as the transistorsare well matched. Thus, before a change in electrochemical status, thelight intensity emitted from sources .76 and 80 will be very nearly thesame. When an electrochemical change in the tissue occurs, the impedancebetween the electrodes of probe 24 will either decrease or increasedepending on the nature of the electrochemical change. AS a result,bridge 28 becomes unbalanced so that points 31 and 33 will havedifferent voltage levels. After amplification, this difference appearsas a difference in intensity .of light sources 76 and 80. The directionin which the im-' pedance of probe 24 changes determines which lightsource will increase in intensity. As an optional feature,

light sources 76 and 80 maybe of different colors so that detectedelectrochemical changes are more noticeable.

' FIG. 3 illustrates an alternative embodiment of the invention havingan output portion that generates an audible signal indicative ofelectrochemical changes. In

FIG. 3 resistors 84 and 86 areconnected respectively to the collectorsof transistors 72 and 74 of FIG. 2. Re- I sistor 8 6 is connectedthrough resistors 88 and 90 to the bases of transistors 92 and 94respectively. A cross coupling network consisting of resistors 96 and 98and capacitors 100 and 102 interconnect the collector of one transistorwith the base of the other and vice versa. Resistors 1'04 and 106interconnect a negative source of power with the collectors oftransistors 92 and 94 respectively, and the parallel combination ofresistor 108 and capacitor 110 interconnect the common emitters oftransistors 92 and 94 with a positive source of power 112 (the positiveside of power supply and function as a temperature stabilizing network.

Transistors 92 and 94 and their associated passive elements form amultivibrator having a frequency of oscillation proportional to thevoltage level applied through resistors 88 and 90. Thus, the frequencyat which the multivibrator oscillates is proportional to the voltagelevel at point 33 and will vary up or down in accordance with theelectrochemical status of the tissue.

I The output of the multivibrator circuit is supplied through resistor114 and capacitor1l6 to the base of PNP transistor 118, The parallelcombination of a temperature stability resistor 120 and a by-passcapacitor 122 interconnect theemitter of transistor 118 with positivepower supply112.'The. collector of transistor 118 is coupled throughtransformer 124 to a speaker 126. Resistors 128 and 130 form a voltagedivider for biasing the base of transistor 118. In operation,

transistor 118 functions as an audio amplifier, supplying the finalstage of audio power to speaker 126. Thus, the multivibrator, audioamplifier and speaker combine to generate an audible signal whosefrequency change indicates electrochemical changes in the plant.

Transistor 132 has its collector coupled to the common point betweenresistor 114 and a capacitor 116 and its emitter coupled to the positivesource of power supply 112. The base of transistor 132 is coupled viaresistor 136 to the negative source of power and RC coupled viacapacitor 134 and resistor 84 to the collector of transistor 72 (of FIG.2). Transistor 132 operates as a transient amplitude gate blocking theaudio output from transistor 92 until it is enabled by a signalindicative of a change in the electrochemical status of the tissue. Thatis, so long as the voltage levelat point 31 of bridge 28 is stable,transistor 132 will be biased into conduction via resistor 136, and,capacitor 134 will block the dc signal coming from point 31. The resultis that transistor 118 is shunted and consequently no audio signal isheard. However, any change in the voltage at point 31 .will becommunicated through capacitor 134 to turn off transistor 132 for someperiod of time determined by the RC time constant of resistor 84 andcapacitor 134. During this time, the audio signal, which will bechanging, may be heard. Although an optional feature, transientamplitude gate 132 avoids a possibly undesirable constant tone output.An audible signal would be heard only during changes in theelectrochemical status of the tissue. 6 FIG. 4'illustrates the inventionused for entertainment or decorative purposes. The circuitry is housedin a cabinet 140 having a transluscent front panel 142. Probe 24 isattached to the leaf of a plant 144 in planter 146. Panel 142 may bewhite or have colored sections that are illuminated by light sources 76and 80 (FIG. 2)

-to indicate changes in resistivity. For example, one half of panel 142might provide a red light and the other half a green light. Changes inrelative brightness of the two colors can be related to plant well-beingand may also provide interesting entertainment. To further enhance theenjoyment of the invention,,both a visual and audio output could beemployed simply by combining the circuitry of FIGS. 2 and 3.

As mentioned previously, low frequency changes in impedance of probe 24may be caused by external factors such as ambient humidity ortemperature. These changes can have amplitudes large enough to unbalancethe bridge to a point where it is no longer sensitive to subtle changesin the electrochemistry of the plant. However, it has been observed thatthe changes due to external influence occur over relatively long periodsof time as compared with changes in the electrochemicalstatus of atissue. For example, most variations due to external factors take atleast one minute and often much longer whereas variations of interestsistance varies inversely to the intensity of light they receive(indicated by A) are used for resistances 150, 152, and 154 in bridge156. Points 158 and 160 correspond with points 31 and 33 of bridge 28and are connected to an amplifier 162 which is in turn connected inseries with a long time constant circuit 164, a light driver 166 and alight source 167. Impedance 168 is comparable to impedance 36 in FIG. 2and is the impedance of probe 24. Imbalances in bridge 156 are detectedbetween points 158 and 160 and are supplied via leads 170 and 172 to thebases of transistors 46 and 48 (in FIG. 2) respectively and via leads174 and 176 to differential amplifier 162. Irnbalances in bridge 156 aretransmitted to amplifier 162 as a difference in voltage. Long timeconstant circuit 164 rejects all of the relatively high frequency signalvariations but passes the relatively low frequency variations to lightdriver 166 which drives light source 167 such that impedances 150, 152and 156 follow changes in impedance 168. For example, if a change inambient humidity causes impedance 168 to increase gradually over arelatively long period of time, light driver 166 will cause light source167 to dim such that impedances 150, 152 and 154 also increase inparallel. The converse occurs when impedance 168 decreases.

What is claimed is: 1. An apparatus for detecting the electrochemicalresponse of a tissue to stimuli, comprising:

sensor means electrically engaging said tissue for sensing theelectrochemical condition thereof;

detector means operatively connected to said sensor means for generatingan electrical signal in response to changes in the electrochemicalcondition of said tissue as communicated by said sensor means;

amplifier means arranged to receive said electrical signal and supply anamplified output signal proportional thereto; and

output means arranged to receive said amplified electrical signal andgenerate an output in response thereto wherein said detector meanscomprises a bridge circuit connected to said sensor such that saidelectrodes and tissue form an impedance leg thereof and said amplifiermeans is connected thereacross such that an imbalance of aid bridge willappear as differential voltage at the input thereto and a long timeconstant circuit coupled between said amplifier and said output meansfor rejecting relatively high frequency signal components passingtherethrough.

2. The apparatus of claim 1 wherein said sensor means comprises a pairof electrodes disposed in electrical contact with said tissue.

3. The apparatus of claim 1 further characterized by means arranged toautomatically adjust said detector means to compensate for relativelylow frequency changes in ambient conditions whereby maximum detectormeans sensitivity is maintained.

4. The apparatus of claim 3 wherein said output means comprises a visualdisplay.

5. The apparatus of claim 4 wherein said visual display is a lightsource whose intensity varies in accordance with the electrochemicalstatus of said tissue.

6. The apparatus of claim 3 wherein said output means comprises an audiosystem for generating an audible sound in response to electrochemicalchanges in 91c 'ssue e apparatus of claim 6 wherein said audio systemcomprises:

an oscillator circuit arranged to oscillate with an I audio frequencyproportional to the output of said amplifier means;

a power amplifier arranged to amplify the output 0 said oscillator; andspeaker means connected to said power amplifier. 8. The apparatus ofclaim 7 further characterized by gate means disposed between saidoscillator and power amplifier and communicable with said amplifiermeans so that variations in signal amplitude at said amplifier enablesaid gate means and allow the output of said oscillator to reach saidpower amplifier.

9. The apparatus of claim 8 further characterized by a light sourceconnected to said amplifier means whereby both an audible and visualresponse are provided.

10. An apparatus for detecting the electrochemical response of a tissueto stimuli, comprising:

sensor means electrically engaging said tissue for sensing theelectrochemical condition thereof;

detector means operatively connected to said sensor means for generatingan electrical signal in response to changes in the electrochemicalcondition of said tissue as communicated by said sensor means;

amplifier means arranged to receive said electrical signal and supply anamplified output signal proportional thereto; and

' output means arranged to receive said amplified electrical signal andgenerate an output in response thereto wherein said output meanscomprises oscillator means arranged to oscillate with an audio frequencyproportional to the output of said amplifier means,

audio transducing means responsive to the output from said output meansand inhibit means responsive to lack of changes in the electrochemicalcondition of said tissue as communicated by said'sensor to inhibitpassage of the output from said oscillator means to said audiotransducing means.

11. The apparatus of claim 10 wherein said detector means comprises abridge circuit connected to said sensor such that said electrodes andtissue form an impedance leg thereof and said amplifier means isconnected thereacross such that an imbalance of said bridge will appearas a differential voltage at the input thereof and a long time constantcircuit coupled between said amplifier and said output means forrejecting relatively high frequency signal components passingtherethrough.

1. An apparatus for detecting the electrochemical response of a tissueto stimuli, comprising: sensor means electrically engaging said tissuefor sensing the electrochemical condition thereof; detector meansoperatively connected to said sensor means for generating an electricalsignal in response to changes in the electrochemical condition of saidtissue as communicated by said sensor means; amplifier means arranged torEceive said electrical signal and supply an amplified output signalproportional thereto; and output means arranged to receive saidamplified electrical signal and generate an output in response theretowherein said detector means comprises a bridge circuit connected to saidsensor such that said electrodes and tissue form an impedance legthereof and said amplifier means is connected thereacross such that animbalance of said bridge will appear as differential voltage at theinput thereto and a long time constant circuit coupled between saidamplifier and said output means for rejecting relatively high frequencysignal components passing therethrough.
 2. The apparatus of claim 1wherein said sensor means comprises a pair of electrodes disposed inelectrical contact with said tissue.
 3. The apparatus of claim 1 furthercharacterized by means arranged to automatically adjust said detectormeans to compensate for relatively low frequency changes in ambientconditions whereby maximum detector means sensitivity is maintained. 4.The apparatus of claim 3 wherein said output means comprises a visualdisplay.
 5. The apparatus of claim 4 wherein said visual display is alight source whose intensity varies in accordance with theelectrochemical status of said tissue.
 6. The apparatus of claim 3wherein said output means comprises an audio system for generating anaudible sound in response to electrochemical changes in the tissue. 7.The apparatus of claim 6 wherein said audio system comprises: anoscillator circuit arranged to oscillate with an audio frequencyproportional to the output of said amplifier means; a power amplifierarranged to amplify the output of said oscillator; and speaker meansconnected to said power amplifier.
 8. The apparatus of claim 7 furthercharacterized by gate means disposed between said oscillator and poweramplifier and communicable with said amplifier means so that variationsin signal amplitude at said amplifier enable said gate means and allowthe output of said oscillator to reach said power amplifier.
 9. Theapparatus of claim 8 further characterized by a light source connectedto said amplifier means whereby both an audible and visual response areprovided.
 10. An apparatus for detecting the electrochemical response ofa tissue to stimuli, comprising: sensor means electrically engaging saidtissue for sensing the electrochemical condition thereof; detector meansoperatively connected to said sensor means for generating an electricalsignal in response to changes in the electrochemical condition of saidtissue as communicated by said sensor means; amplifier means arranged toreceive said electrical signal and supply an amplified output signalproportional thereto; and output means arranged to receive saidamplified electrical signal and generate an output in response theretowherein said output means comprises oscillator means arranged tooscillate with an audio frequency proportional to the output of saidamplifier means, audio transducing means responsive to the output fromsaid output means and inhibit means responsive to lack of changes in theelectrochemical condition of said tissue as communicated by said sensorto inhibit passage of the output from said oscillator means to saidaudio transducing means.
 11. The apparatus of claim 10 wherein saiddetector means comprises a bridge circuit connected to said sensor suchthat said electrodes and tissue form an impedance leg thereof and saidamplifier means is connected thereacross such that an imbalance of saidbridge will appear as a differential voltage at the input thereof and along time constant circuit coupled between said amplifier and saidoutput means for rejecting relatively high frequency signal componentspassing therethrough.